Chapter 4Chapter 4

Aqueous Reactions and Solution Aqueous Reactions and Solution StoichiometryStoichiometry

Pg 105Pg 105

Aqueous SolutionsAqueous Solutions

-Aqueous Solutions are solutions that have water as the dissolving medium.

-Many reactions contain substances that have been dissolved in water, making them aqueous solutions.

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3 Main Major Chemical 3 Main Major Chemical Reaction Types Involving Reaction Types Involving

Aqueous SolutionsAqueous Solutions

Precipitation ReactionsPrecipitation Reactions Acid-Base ReactionsAcid-Base Reactions

Redox ReactionsRedox Reactions

4.1 General Properties of 4.1 General Properties of Aqueous SolutionsAqueous Solutions

Solutions are homogeneous mixturesSolutions are homogeneous mixtures Usually has more solvent than solute.Usually has more solvent than solute. Solute is the substance being dissolved in Solute is the substance being dissolved in

the solventthe solvent

Electrolytic PropertiesElectrolytic Properties

Pure water is a bad conductorPure water is a bad conductor The presence of Ions in water makes it into a The presence of Ions in water makes it into a

good conductorgood conductor Aqueous solution that conduct electricity such as Aqueous solution that conduct electricity such as

NaClNaCl(aq)(aq) or other ionic compounds are electrolyte. or other ionic compounds are electrolyte.

Solutions that do not form ions like sucrose and Solutions that do not form ions like sucrose and other molecular compounds are nonelectrolytes.other molecular compounds are nonelectrolytes.

Ionic Compounds in WaterIonic Compounds in Water

Ionic compounds dissolve in water dissociating Ionic compounds dissolve in water dissociating into component ions (ex. NaCl -> Nainto component ions (ex. NaCl -> Na++&Cl&Cl--))

The polar nature of water makes it a very The polar nature of water makes it a very effective solventeffective solvent

The polarity helps prevent anions and cations The polarity helps prevent anions and cations from rejoining.from rejoining.

Molecular Compounds in Molecular Compounds in WaterWater

Structure usually remains unchanged, they Structure usually remains unchanged, they usually do not form ionsusually do not form ions

Acids and a few other compounds like Acids and a few other compounds like ammonia react with water forming ions ammonia react with water forming ions making an electrolyte.making an electrolyte.

Ex. HCl make HEx. HCl make H++ and Cl and Cl- - ions ions

Strong & Weak ElectrolytesStrong & Weak Electrolytes

Strong Electrolytes = Most ionic Strong Electrolytes = Most ionic compounds and a few molecular compounds and a few molecular compounds.compounds.

Weak Electrolytes = Molecular compounds Weak Electrolytes = Molecular compounds that produce few ions when dissolvedthat produce few ions when dissolved

If the chemical reaction goes both ways, If the chemical reaction goes both ways, breaking into ions, and recombining, than breaking into ions, and recombining, than the substance is a weak electrolyte. the substance is a weak electrolyte.

HClHCl(aq)(aq) --> --> HH+ + + Cl+ Cl--

One arrow means strong One arrow means strong electrolyteelectrolyte

HC2H3O29(aq) <--> H+ + C2H3O2-

Double arrow means weak electrolyte

4.2 Precipitation Reactions4.2 Precipitation Reactions

Precipitation Reaction = Reactions that Precipitation Reaction = Reactions that result in the formation of an insoluble result in the formation of an insoluble product.product.

Precipitate = Insoluble solid formed by a Precipitate = Insoluble solid formed by a reaction in a solutionreaction in a solution

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Solubility Guidelines for Ionic Solubility Guidelines for Ionic CompoundsCompounds

Solubility = Amount of substance that can be Solubility = Amount of substance that can be dissolved in given amount of solventdissolved in given amount of solvent

If less than .01 mol dissolves in a liter, If less than .01 mol dissolves in a liter, substance is insoluble. In these substances substance is insoluble. In these substances intermolecular attraction is stronger than the intermolecular attraction is stronger than the waters polarity.waters polarity.

Table 4.1 pg 111 (Solubility Guidelines for Table 4.1 pg 111 (Solubility Guidelines for Common Ionic Compounds in Water)Common Ionic Compounds in Water)

All ionic compounds with 1A elements or All ionic compounds with 1A elements or ammonia ions are soluble in water.ammonia ions are soluble in water.

Is Sodium Carbonate SolubleIs Sodium Carbonate Soluble(Na(Na22COCO33))

Yes. Carbonate is usually insoluble, but Yes. Carbonate is usually insoluble, but when paired with a 1A element, Sodium, when paired with a 1A element, Sodium, the compound becomes soluble.the compound becomes soluble.

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Exchange (Metathesis) Exchange (Metathesis) ReactionsReactions

Exchange or Metathesis Reaction = Exchange or Metathesis Reaction = AX+BY --> AY+BXAX+BY --> AY+BX

Precipitation and Acid Base Reactions Precipitation and Acid Base Reactions conform to this patternconform to this pattern

What precipitate forms when What precipitate forms when BaClBaCl22 and K and K22SOSO44 are mixed? are mixed?

BaSOBaSO4, 4, SOSO442-2- is soluble but Ba is soluble but Ba2+2+ is not is not

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Ionic EquationsIonic Equations

Molecular Equation = complete chemical Molecular Equation = complete chemical formulas of reactants and productsformulas of reactants and products

Complete Ionic Equation = All Soluble Complete Ionic Equation = All Soluble strong Electrolytes are shown as ionsstrong Electrolytes are shown as ions

Spectator ions = ions that are present in Spectator ions = ions that are present in the same form on both product and the same form on both product and reactant side. These are dropped out to reactant side. These are dropped out to form a Net Ionic Equation.form a Net Ionic Equation.

Steps to Write a Net Ionic Steps to Write a Net Ionic EquationEquation

Write a balanced Molecular EquationWrite a balanced Molecular Equation Rewrite to show ions that are formed Rewrite to show ions that are formed

during dissociation or ionization, only the during dissociation or ionization, only the strong electrolytes are written in ionic formstrong electrolytes are written in ionic form

Cancel spectator ions on both sidesCancel spectator ions on both sides

Write the net ionic equation Write the net ionic equation for the mixing of CaClfor the mixing of CaCl2 2 and and

NaNa22COCO33

CaClCaCl2(aq) 2(aq) + Na+ Na22COCO3(aq)3(aq) --> CaCO --> CaCO3(S)3(S) + 2NaCl + 2NaCl(aq)(aq)

CaCa2+2++ 2Cl+ 2Cl-- + 2Na + 2Na++ + CO + CO332-2--->CaCO-->CaCO3(s)3(s) + 2Na + 2Na++ + +

2Cl2Cl--

CaCa2+2+(aq) (aq) + CO+ CO33

2-2-(aq)(aq)-->CaCO-->CaCO3(s)3(s)

Acid-Base ReactionsAcid-Base Reactions

Acids and Bases are common ElectrolytesAcids and Bases are common Electrolytes

Are some of the most common compounds we Are some of the most common compounds we encounterencounter

AcidsAcids

Substances that ionize in aqueous solutions Substances that ionize in aqueous solutions upping Hupping H++ concentration concentration

Protic refers to amount of HProtic refers to amount of H++ ions ionizing. ions ionizing. Monoprotic = 1, Diprotic = 2.Monoprotic = 1, Diprotic = 2.

Diprotic Acid ionization occurs in two steps, One Diprotic Acid ionization occurs in two steps, One hydrogen is separated at a time.hydrogen is separated at a time.

BasesBases

Substances that accept HSubstances that accept H++ ions, or increases OH ions, or increases OH-- concentration.concentration.

Does not need to have an OHDoes not need to have an OH- - ion, if accepts Hion, if accepts H++ like NHlike NH33 (ammonia is a weak electrolyte) (ammonia is a weak electrolyte)

Strong and Weak Acids and Strong and Weak Acids and BasesBases

Strong Acids and Bases are strong electrolytes Strong Acids and Bases are strong electrolytes that completely ionize in solutionsthat completely ionize in solutions

Weak Acids and Bases are electrolytes that partly Weak Acids and Bases are electrolytes that partly ionize in solutionsionize in solutions

Table 4.2 pg 115 (Common Strong Acids and Table 4.2 pg 115 (Common Strong Acids and Bases)Bases)

Identifying Strong and Weak Identifying Strong and Weak ElectrolytesElectrolytes

Is the compound ionic, yes -> probably strong Is the compound ionic, yes -> probably strong electrolyteelectrolyte

Not ionic, is it an acidNot ionic, is it an acid Yes, is an acid, if strong, is a strong electrolyte if Yes, is an acid, if strong, is a strong electrolyte if

weak, is a weak electrolyte.weak, is a weak electrolyte. Not an acid, is it NHNot an acid, is it NH33 or another molecular base, or another molecular base,

yes -> weak base, no -> probably nonelectrolyteyes -> weak base, no -> probably nonelectrolyte

Classify HNOClassify HNO3 3 as a strong, as a strong,

weak, or non Electrolyteweak, or non Electrolyte

StrongStrong HNOHNO33 is a strong acid making it a strong is a strong acid making it a strong

electrolyte.electrolyte.

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Neutralization Reactions and Neutralization Reactions and SaltsSalts

When acid and base react together, it is a When acid and base react together, it is a neutralization reaction.neutralization reaction.

These reactions form a salt and a water.These reactions form a salt and a water. Salt = any ionic compound whose cation comes Salt = any ionic compound whose cation comes

form a base and anion comes from an acid.form a base and anion comes from an acid.

Write the net ionic equation Write the net ionic equation for HCfor HC22HH33OO2 2 and Ba(OH)and Ba(OH)22

HCHC22HH33OO2(aq)2(aq)+OH+OH--(aq)(aq)--> H--> H22OO(l)(l) + C + C22HH33OO22

--(aq)(aq)

Acid-Base Reaction with Gas Acid-Base Reaction with Gas FormationFormation

The sulfide ion and carbonate ion react with The sulfide ion and carbonate ion react with acids to form gasesacids to form gases

2HCl2HCl(aq)(aq) + Na + Na22SS(aq)(aq) --> H --> H22SS(g)(g)+2NaCl+2NaCl(aq)(aq)

HClHCl(aq)(aq)+NaHCO+NaHCO3(aq)3(aq)-->NaCl-->NaCl(aq) (aq) + H+ H22OO(l)(l)+CO+CO2(g)2(g)

4.4 Oxidation - Reduction 4.4 Oxidation - Reduction ReactionsReactions

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Oxidation and ReductionOxidation and Reduction

Metals undergoing erosion are losing Metals undergoing erosion are losing electrons and forming cationselectrons and forming cations

Loss of electrons is known as oxidizationLoss of electrons is known as oxidization The gain of electrons by a substance is The gain of electrons by a substance is

called reductioncalled reduction

Oxidation NumbersOxidation Numbers

Oxidization number is the actual charge of the of Oxidization number is the actual charge of the of the atom.the atom.

In elemental form the Oxidization number is 0In elemental form the Oxidization number is 0 Oxidization of monatomic ions equals the chargeOxidization of monatomic ions equals the charge Nonmetals are usually negative, Oxygen usually Nonmetals are usually negative, Oxygen usually

is -2, Hydrogen is +1, Fluorine is -1.is -2, Hydrogen is +1, Fluorine is -1. Sum of oxidation numbers in neutral compound Sum of oxidation numbers in neutral compound

is 0 or equal to the charge in a polyatomic ion.is 0 or equal to the charge in a polyatomic ion.

Determine the oxidation stat Determine the oxidation stat of sulfur in Hof sulfur in H22SS

-2, Hydrogen is always +1 2H = +2 so S = -2 so -2, Hydrogen is always +1 2H = +2 so S = -2 so that sum of oxidation numbers = 0that sum of oxidation numbers = 0

Oxidation of Metals by Acids Oxidation of Metals by Acids and Saltsand Salts

Displacement Reactions = ion is solution is Displacement Reactions = ion is solution is displaced or replaced through the oxidation of displaced or replaced through the oxidation of an element.an element.

A+BX-->AX+BA+BX-->AX+B

Write the net ionic equation Write the net ionic equation for the reaction of aluminum for the reaction of aluminum

and hydrobromic acidand hydrobromic acid

2Al2Al(S) (S) + 6H+ 6H++(aq)(aq)+6Br+6Br---->2Al-->2Al3+3+

(aq)(aq)+6Br+6Br--(aq)(aq)+3H+3H2(g)2(g)

2Al2Al(s)(s)+6H+6H++(aq)(aq)-->2Al-->2Al3+3++3H+3H2(g)2(g)

The Activity SeriesThe Activity Series

Table 4.5 pg 124 Activity Series of Metals in Table 4.5 pg 124 Activity Series of Metals in Aqueous SolutionAqueous Solution

Is a table of metals arranged in order of Is a table of metals arranged in order of decreasing ease of oxidation.decreasing ease of oxidation.

Alkali and Alkaline Earth Metals are at the Alkali and Alkaline Earth Metals are at the top.top.

Metals on the list can be oxidized by any of Metals on the list can be oxidized by any of the ions below them.the ions below them.

Can Pb(NOCan Pb(NO33))2 2 can oxidize Zn, can oxidize Zn,

Cu, or FeCu, or Fe

Zn and FeZn and Fe Refer to table 4.5Refer to table 4.5

4.5 Concentrations Of 4.5 Concentrations Of SolutionsSolutions

Concentration = Amount of solute dissolved Concentration = Amount of solute dissolved in a given quantity of solvent or solution.in a given quantity of solvent or solution.

MolarityMolarity

Molarity (M) = (moles of solute)/(Volume of Molarity (M) = (moles of solute)/(Volume of Solution in Liters)Solution in Liters)

Calculate the molarity of a Calculate the molarity of a solution made by dissolving solution made by dissolving 23.4 g of sodium sulfate in 23.4 g of sodium sulfate in

enough water to form 125ml enough water to form 125ml of solutionof solution

23.4g*(1mol Na23.4g*(1mol Na22SOSO44/142g Na/142g Na22SOSO44) = .165 ) = .165 molsmols

125ml*(1L/1000ml)=.125125ml*(1L/1000ml)=.125 .165mols Na.165mols Na22SOSO44/.125L = 1.32M/.125L = 1.32M

DilutionDilution Adding water to lower the concentration is called Adding water to lower the concentration is called

dilutiondilution MMii*V*Vii=M=Mff*V*Vf f i = initial f = final M = Molarity V= Volume i = initial f = final M = Molarity V= Volume

How many mL of 3.0 M How many mL of 3.0 M HH22SOSO44 are required to make are required to make

450 mL of .10 M H450 mL of .10 M H22SOSO44 ? ?

VVii = (M = (MffVVff)/M)/Mii

((.10M)(450mL))/3.0M = 15 mL((.10M)(450mL))/3.0M = 15 mL

4.6 Stoichiometry and 4.6 Stoichiometry and Chemical AnalysisChemical Analysis

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TitrationsTitrations

Second solution of known concentration is called the Second solution of known concentration is called the standard solutionstandard solution

Combining the standard solution with a solution of Combining the standard solution with a solution of unknown concentration to get a chemical reaction is unknown concentration to get a chemical reaction is called titrationcalled titration

Equivalence point is where equivalent quantities have Equivalence point is where equivalent quantities have been brought together indicators change the color been brought together indicators change the color helping us to find this point.helping us to find this point.

If molar ratio is 1 to 1 you may use the dilution equation.If molar ratio is 1 to 1 you may use the dilution equation. If not, convert standard solution to mols, then use molar If not, convert standard solution to mols, then use molar

ratio to give you the mols of the unknown,ratio to give you the mols of the unknown, then convert then convert to grams.to grams.

How many grams of chloride ion are in How many grams of chloride ion are in the sample of the water if 20.2 mL of .1 M the sample of the water if 20.2 mL of .1 M

Ag is required to react with all the Ag is required to react with all the chloride in the sample?chloride in the sample?

(20.2 mL solution) * (1L/1000mL solution) * (.1mol Ag(20.2 mL solution) * (1L/1000mL solution) * (.1mol Ag++/L solution) = 2.02 /L solution) = 2.02 * 10* 10-3-3

1mol Ag1mol Ag++ : 1mol Cl : 1mol Cl--

(2.02*10(2.02*10-3-3 mol Cl mol Cl--) * (35.5g Cl) * (35.5g Cl--/1 mol Cl/1 mol Cl--) = 7.17 * 10) = 7.17 * 10-2-2 g Cl g Cl--